Method of making commutators



METHOD OF MAKING COMMUTATORS Filed May 18, 1944 IN VEN TOR.

' Patented May 21, 1 946 YMETHOD F MAKING COMMUTATORS Carl it.Meyerhoefer, Brooklyn, N. Y., asslgnor to E. A. Laboratories, Inc.,Brooklyn, N. Y., a corporation of New York AppllcationMay 18, 1944,Serial No. 536,079

3 Claims.

This invention relates to improvements in the construction ofcommutators for electric motors and generators.

In particular, the. invention relates to an improved commutator for usewith relatively small, high speed motors, and allords means whereby acommutator having a high degree of perfection of finish and balance maybe made by massproduction methods, with relatively unskilled labor.

It is an object oi! the invention to provide an improved means ofmanufacturing commutators for electric motors or generators.

It is an object of the invention to provide a method of manufacturingcommutators, which will afford a low-cost, high quality product.

It is an object of the invention to provide a' method of manufacturingcommutatore by the cold working of sheet copper, whereupon the iinishedproduct is work-hardened and therefore of increased durability.

Commutators for relatively small-size motors are presently made byplacing within a tubular blank of copper having interiorly directedfingers or tabs, a mass of moldable insulation material, curing saidmaterial in situ and then slitting the cylinder according to the numberof poles of the varmature with which the commutator is tovbe used. i

A second presently known method ot manufacture resides in rolling astrip of copper, congurated to provide a plurality of fingers orsoldering lugs, into cylindrical form, iiliing the cylinder withinsulation material as aforesaid, and slitting the cylinder asaforesaid.

Disadvantages in. the said methods reside in the necessity of usingrelatively soft copper stock to. insure that the fingers and lugs do notbreak or fracture during the bending thereof; in manuiacturingaccordingto the rolled-strip method,

. it is diflicult to attain an initial cylinder which is trulyconcentric, necessitating grinding or turnn ing operations which resultin portions which are relatively thinner than others. In high speedmotors, in which 12,500 R. P. M. is not an unusual speed, 'an unbalancedcondition, such as will result from non-uniform weight distribution, isdetrimental to operative life.

Pursuant to the present invention, a nat blank of soft or semi-softcopper is drawn, in the cold,

into cup shape, slightly oversize, and having a,

plurality of axial tabs at itsopen end, A light anneal slightly softensthe metal to protect against breakage of the tabs upon the bendingthereof; successive cold-working stages provide Ztl-155.54

a commutator blank of work-hardened copper. The blank may subsequentlybe provided with a core of phenolic condensation material or the like,slotted to provide the requisite poles, and

mounted on its armature shaft for polishing.

During the cupping and drawing operations, the blank is maintained as asubstantially true cylinder, and the grinding and polishing of the Fig,1 is a plan view of a soft copper sheet, l

blanked to provide the terminal tabs and anchoring tabs of the completedcommutator;

Fig,I 2 is a side elevation of the same;

Fig. 3 is a side elevation, in section, oi the nrst clipping stage ofthe copper sheet;

Fig. 4 is an end elevation of the same;

Fig. 5 is a front view of the commutator blank at a successive stage ofmanufacture;

Fig. 6 is a side elevation, in section, of the commutator blank of Fig.5;

Fig. 7 ,is a side elevation, in section, of the commutator blank,showing the bending of the terminal and anchoring tabs;

Fis. 8 is a rear elevation of the commutator blank ol Fig. 7;

Fig. 9 illustrates the next forming stage of the commutator blank;

Fig. l0 depicts the tinned commutator blank of Fig. 9, prior to thestage oi the insertion of dielectric material therein;

Fig, 11 shows, in section, a commutator blank complete as respects thecore of dielectric material therein; and

Fig. l2 is asection on lines it-ii of Fig. ll, after the slittingoperation.

Referring to the drawing, a blank l@ is stamped from copper sheet.Extensions il, l2, ultimately provide soldering tabs and anchoring lugs,respectively.

The blank is placed in a conventional cupping or draw press and is drawnto produce a com mutator shell lila, in which the respective tabs il, l2are axially disposed. The drawing oper ation affords a symmetrical,closed-ended cylin der, preferably .005 inch oversize.

The closed end i3 of the shell lila is blanked out to provide aplurality of anchoring lugs lil.

If desired, the commutator` shell, now desigfnated lb, may be given alight anneal which conditions the copper so that the soldering tabs Iland the anchoring lugs I2 may be angularly struck, see Fig. 7. withoutdanger of fracture.

Subsequently, and preferably in a cold working drawing operation, therespective anchoring lugs i2 and I4 are directed inwardly of the shell,identified Ilic, as shown in Fig. 9. At this stage, the initial oversizedimension Illa may be re duced as desired. The respective anchors i2 andI4 are equal in .number and are substantially oi equal weight. As shownin Fig. 8, the disposition of the anchors I2 and Il is such as toprovide clear areas Ila adjacent each soldering tab Il, along which theslitting saw may pass ina later stage.

The shell Ic is then plated with a thin coating Il of tin. In a suitablemolding press (not shown) the shell luc is disposed concentrically abouta bushing It, the inside diameter of which is suitable to engage tightlythe shaft of the armature with which the commutator is to be used, andthe annular space about said shell is filled with a thermo-settingplastic material I1 such as "Bakelite" or thelike, whereupon the plasticmaterial is cured, bonding with the sleeve Il, and completely envelopingand engaging the anchors I2 and il.

The thus-formed shell ild is disposed on a suitabe slit-ting machine(not shown) and is subdivided into mutually insulated commutatorsegments I8, symmetrical and concentric with respect to the bushing Il,and each embodying a soldering tab Il and anchor means i2 and il. Eachsegment is therefore of substantially uniform weight and the dynamicbalance f the commutator is preserved.

It will be understood that for smaller or lower speed motors, one of theanchoring tabs may be omitted from each segment, although there islittle advantage gained from so doing.

It will be noted that at this stage, the tin plating Il remains on thecommutator.

The commutator is then placed on the previously trued armature shaft,for secdrement thereto, and the leads to the respective pole windings ofthe armature soldered to the soldering tabs Il. The tin coating on thetabs Il simplies the soldering step. The thus-mounted commutator is thenground to remove the sur plus tin coating and to polish the surface ofthe respective segments. It will be apparent that with the commutatormounted upon the previously trued armature shaft, the symmetry ofposition of the segments with respect to the shafts is insured.

Whereas it is obvious that the several cbjects of the invention asspecifically aforenoted are achieved, it 1s apparent that numerouschanges in the manner of performing the steps of the method, andvariations of the sequence of performance thereof might be resorted towithout departing from the spirit of the invention as defined by theclaims.

Iclaim:

1. A method of manufacturing commutators, which includes the steps of:drawing an initially circular blank having a plurality of pairs ofradial extensions. into closed-ended cylindrical form having a diameterlarger than the final commutator diameter, saidcylindrical form havingsaid extensions projecting axially thereof; blanking out the said closedend to provide thereat, a plurality of tabs equal in number to one halfof the said pairs of extensions; cold working said cylinder to reducethe diameter thereof while bending one extension of each of said pairsof extensions angularly inwardly of the cylinder and bending theremaining extension angularly outwardly; bending the said tabs angularlyinwardly of said cylinder; disposing within said cylinder a mass ofinsulation material in bonded relationship with said inwardly directedelements; slitting the cylinder longitudinally adjacent each of the saidoutwardly directed extensions to subivide the cylinder into a pluralityof equal, electrically insulated segments of the said cylinder; and subsequently smoothing the surface of the said segments.

2. A method of manufacturing commutators which includes the steps ofdrawing a blank of metal having a plurality of pairs of radialextensions, into closedended cylinder form; blanking out the said closedend to provide a plurality of tabs equal in number to one half of thesaid pairs of extensions; annealing the said cylinder to soften thesame; cold-working the cylinder to reduce the diameter thereof, whiledisplacing one of each of said pairs of extensions angularly inwardly ofthe cylinder; displacing the tabs formed at the initially closed end ofsaid cylinder angularly inwardly thereof; disposing within the saidcylinder a sleeve of less diameter than the cylinder; disposing andcuring within said cylinder and about said sleeve a mass ofthermo-setting insulating material in bonded relationship with theinwardly projecting tabs and with the exterior wall of said sleeve;slitting said cylinder axially throughout its length at equi-distantlocations without slitting the said tabs or extensions to subdivide thecylinder into a plurality of mutually insulated equi-angular segments;and smoothing the surface of the said segments.

3. The method of manufacturing commutators, which includes the steps ofcold-working an initially fiat blank of metal into a cylinder having` aplurality of equi-angularly spaced tabs extending outwardly therefrom atone end thereof and a plurality of adjacent tabs extending angularlyinwardly of said cylinder; tin plating the said cylinder and theoutwardly extending tabs thereof; disposing within said cylinder a massof insulation material; bonding the said mass of material to the innerwall of said cylinder and to the said inwardly directed tabs, andsubdividing said cylinder into a plurality of individual segments ofequal area and substantially equal weight and removing the tin platingfrom the surface of said segments by grinding the segments to produce asmooth surface thereon, while leaving the tin plating on the said tabs.

CARL E. MEYERHOEFER.

